A because they do not occur in all chordates b because

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ause they do not occur in all chordates. b)! Because they evolved convergently in hemichordates and cephalochordates. c)! Because they have been further modified within the chordates. d)! Because they occur in other deuterostomes. dorsal tubular nerve cord neural plate begins to dip inward and the side begins to come up become spinal cord edges closes and neural tube detach from the ectoderm later it spread away spinal bifida: disorder of the neural tube development Urochordates or tunicates •! sea squirts (ascidians) and relatives •! sea squirts are bag-like, with enlarged perforated pharynx for filter-feeding Why a chordate? Because urochordate larvae show all the chordate characters 1.! 2.! 3.! 4.! notochord dorsal hollow nerve postanal tail endostyle/thyroid Is this an ancestral urochordate body plan? sessile Free...
View Full Document

This document was uploaded on 04/13/2013.

Ask a homework question - tutors are online